Use a direct include of strings headers in chrome/browser/r*-s*/.

chrome/browser/signin/signin_ui_util.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_SIGNIN_SIGNIN_UI_UTIL_H_
 #define CHROME_BROWSER_SIGNIN_SIGNIN_UI_UTIL_H_
 
-#include "base/string16.h"
+#include "base/strings/string16.h"
 
 class GlobalError;
 class Profile;
 class SigninManagerBase;
 
 // Utility functions to gather status information from the various signed in
 // services and construct messages suitable for showing in UI.
 namespace signin_ui_util {
 
 // If a signed in service is reporting an error, returns the GlobalError
 // object associated with that service, or NULL if no errors are reported.
 GlobalError* GetSignedInServiceError(Profile* profile);
 
 // Return the label that should be displayed in the signin menu (i.e.
 // "Sign in to Chromium", "Signin Error...", etc).
 string16 GetSigninMenuLabel(Profile* profile);
 
 void GetStatusLabelsForAuthError(const SigninManagerBase& signin_manager,
                                  string16* status_label,
                                  string16* link_label);
 
 }  // namespace signin_ui_util
 
 #endif  // CHROME_BROWSER_SIGNIN_SIGNIN_UI_UTIL_H_